rsnext/errors/invalid-route-source.md
Damien Simonin Feugas d8395e4eeb
docs: more detailed error message when failing to parse a middleware matcher (#41390)
## 📖 What's in there?

This is a follow-up for https://github.com/vercel/next.js/pull/40180
Someone made the good point that users may get directed to this error page while setting up middleware matchers. And that page has no information (yet) about it.

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm lint`
- [x] The "examples guidelines" are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)



Co-authored-by: Balázs Orbán <18369201+balazsorban44@users.noreply.github.com>
2022-10-13 18:03:10 +00:00

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Markdown

# Invalid Custom Route `source`
#### Why This Error Occurred
When defining custom routes, or a middleware `matcher`, a pattern could not be parsed.
This could have been due to trying to use normal `RegExp` syntax like negative lookaheads (`?!exclude`) without following [`path-to-regexp`](https://github.com/pillarjs/path-to-regexp)'s syntax for it.
#### Possible Ways to Fix It
Wrap the `RegExp` part of your `source` as an un-named parameter.
---
Custom routes:
**Before**
```js
{
source: '/feedback/(?!general)',
destination: '/feedback/general'
}
```
**After**
```js
{
source: '/feedback/((?!general).*)',
destination: '/feedback/general'
}
```
---
Middleware:
**Before**
```js
const config = {
matcher: '/feedback/(?!general)',
}
```
**After**
```js
const config = {
matcher: '/feedback/((?!general).*)',
}
```
### Useful Links
- [path-to-regexp](https://github.com/pillarjs/path-to-regexp)
- [un-named parameters](https://github.com/pillarjs/path-to-regexp#unnamed-parameters)